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A variable is a letter that represents a number. An expression that contains at least one variable is called variable expression, also called algebraic expression. A variable expression has one or more terms. A term is a number, a variable, or a product of numbers and variables. For example,
3(x^2)y + 2xy + x - 7 is a variable expression, where you have 4 terms.
When working with variable expression, you often use the substitution principle:
If a = b, then a may be replaced by b in any expression.
The set of numbers that a variable may be represent is called replacement set, or domain, of the variable. To evaluate a variable expression, you replace each variable with one of its values and simplify the numerical expression that results.
Example: Evaluate the expression 2x - 4y for x = 5 and y = -9.
Solution:
2x - 4y
= 2(5) - 4(-9)
= 10 + 36
=46
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What do you call replacing a variable in an in a algebraic expression with a quantiy?
When you replace a variable with a quantity, it is called a substitution.
How do you evaluate an algebraic expression?
You have to substitute a value for the letter variable in the expression. This is what we call evaluating the algebraic expression. An example would be 3x+1=7, when x=2.
What do you call a number in front of a variable?
Like the 7 in the expression 7x? If so that is called the coefficient.
What do you call a letter that stands for a number in an equation?
It is called a variable
What is twice a number plus 27 in an algebraic expression?
Twice a number can be represented as 2x, where x is the unknown number. Adding 27 to this expression gives 2x + 27. Therefore, "twice a number plus 27" can be written as the algebraic expression 2x + 27.
